Effect of circulating factors on cerebral artery function during hyperglycemic stroke

Abstract

We investigated the influence of circulating factors on vascular function of middle cerebral arteries (MCA) as a potential mechanism controlling perfusion and stroke outcome during hyperglycemic stroke. Nonischemic MCA were isolated from male Wistar rats, cannulated and perfused with plasma (20% in buffer) from rats that were hyperglycemic by STZ (50mg/kg) for 5 days and that underwent either MCA occlusion (MCAO) for 2 hrs with 2 hrs reperfusion (MCAO, n=8) or a 4 hour sham procedure (Sham, n=8). Control vessels were perfused with buffer without plasma (CTL, n=8). Myogenic responses and constriction to NOS inhibition by a single concentration (0.1mM) of L‐NNA were compared. Arteries perfused with Sham and MCAO plasma had significantly increased myogenic tone vs. CTL (at 75mmHg: 30±3 and 22±4% vs. 10 ±3%;p<0.01 vs. CTL). Sham and MCAO plasma vessels also had smaller lumen diameters vs. CTL (at 75mmHg: 210±14μm and 193±9μm vs. 243±9μm; p<0.05). Constriction to L‐NNA was decreased only in the MCAO plasma group. The percent constriction to L‐NNA for CTL, Sham and MCAO plasma was: 41±5%, 31±5% (ns) and 4±1% (p<0.01 vs. both). These results suggest that circulating factors in plasma during postischemic reperfusion increase tone in MCA possibly through an effect on NO. Further experiments are needed to determine what circulating factors are in both types of plasma that affect tone. Supported by RO1NS043316 and PO1HL9548801.

The vascular Na,K-ATPase: clinical implications in stroke, migraine, and hypertension

“…Previous studies in rats indicate an increased vascular tone of rat arterioles after ischemic stroke [ 100 , 115 ]. This increased arteriolar tone is not associated with changed smooth muscle cell membrane potential nor changed intracellular Ca 2+ concentration compared with rats undergoing sham surgery [ 100 ].…”